Zirconium-manganese steel



Patented Feb. 28, 1928.

V UNITED STATES PATENT OFFICE.

FREDERICK M. IBECI KE'I', OF NEW YORK, N. Y., A SSIGNOR TOELEGTRO METALLURGICAL COMPANY, A GORPOBATION OF WEST VIRGINIA.

ZIRCONIUM-MANGAN ESE STEEL.

No Drawing in small proportions, say up to0.5% or some- W what higher, the manganese being usually introduced as a deoxidizer and to counteract the red-shortness due to sulfur, and having in these small proportions little or no significance as an alloying metal. True man- 35 ganese steels of the Hadfield type, containing around 12% or 13% manganese and characterized by extraordinary toughness and hardness are also well known. More recently steels of manganese content inter- 2 mediate these extremes have come into use, the manganese usually lying between 1% and 2%,and the carbon varying from fractional quantities up to about 1%. Such steels, especially those of relatively low carbon content (for example around 0.3% car bon), possess high tensile strength and toughness. i

It is now well known that zirconium, added in small proportions, say 0.15% to 0.50%, has a marked beneficial effect upon certain steels, both of the plain carbon and alloy types. the contrary, no beneficial action of zirconium has been observed.

My investigations of the manganese steels have disclosed a pronounced beneficial action of zirconium in'the case of those steels above mentioned which contain manganese in the proportions of about 1% to 2%, or slightly 40 below or above these limits, carbon being below about 1%. So far as my' investigations have shown, this marked action of zirconium, which is best evidenced by the increase in shock resistance of the steels as measured by the Izod test, is characteristic of these particular manganese steels. Similar effects have not been observed with manganese either substantially above or substantially below theabove range. The optimum- 5 results as regards shock resistance have been obi iined with 'steels containing carbon arc and 0.3% with manganese about 1.25%, although my invention is of course not restricted to this particular composition.

With certain other steels, on-

Application filed July 9, 1926. Serial No. 121,495. V

, The effects of zirconium on the physical properties of certain steels within the range contemplated by this invention are illustrated in the tests tabulated below. In these tests the zirconium, in the form of commercial zirconium-silicon alloy, was added to the molten steel before casting, in the following manner:

The steels were melted in a basic lined electric steel-meltin furnace, and when properly finished and ready for casting, zirconium-silicon was added to a portion of each steel in quantity corresponding to an addition of 0.20% Zr. To another ladle of the same steel, an identical quantity of silicon was added as ferrosilicon. The steels were then cast into ingots, forged, rolled and heat-treated simultaneously and in identical manner.

In connection with the foregoing table it may be explained that the Merit index is an arbitrary value which has been used by metallurgists in an attempt to grade steels, and is calculated from the data obtained in the so-called static tensile test. Naturally the significance of this index must be considered with respect to some particular application of the steel.

It will be noted that the shock resistance in the zirconium treated steels, as measured All steels were tested in the aircooled condition. i

by the Izod test, has in these particular cases been increased by some 70 or 80% of its'value in the untreated steels; and I have found a similar increase of at least 20%, and usually upward of 50%, for the entire range of compositions contemplated by this invention. It will also be noted that this increase in shock value has been secured without sacrifice of other valuable properties. Particularl in the higher carbon ranges, for example a ove 0.35%, or in steels of relatively lower ductility, the zirconium treatment brings about a pronounced improvement in ductility.

While the amounts of zirconium necessar to produce these efiects are small, and a though the manner in which zirconium acts has not as yet been certainly determined, it is regarded as preferable, if not essential, that the quantity of zirconium used should be sufliclent so that a determinable amount exists in the finished steel. This was the case with each of the specific steels of which the pro erties are listed above.

y investigations indicate that the principal application of the invention will be to steels containing not more than about 0.7% carbon. It also appears that when the manganese' content is toward the upper limit 'ven, viz, at about 2.0%, themaximum car 11 content referred to herein should not be incor orated. The best results have been obtains with steels wherein the sum of the carbon and manganese does not exceed 2.5%.

Steels having the chemical composition described herein acquire on air-cooling only a moderate degree of hardness and strength. Thus, in the specific examples tabulated, the tensile strength of the air-cooled steel does not exceed 125,000 pounds per square inch. The beneficial eifect of zirconium on the ductility of steel is already known in connection with carbon and alloy steels heat-treated to impart to' them a high degree of hardness and strength, but the prior art indicates that when the same steels are heat-treated to impart lower strength and hardness, as b quenching followed by drawing at 450 or higher a content of zirconium .does not increase the Izod number. In Patent No. 1,546,881 I have shown the effect of zirconium in raising the impactnumber of high ghosphorus steels in the annealed condition.

0, far as I am aware the resent invention constitutes the first case w ere a zirconium content has been shown to increase materially the Izod number of a steel having a normal phosphorus content and a tensile strength less than 125,000 pounds per square inch.

I claim:

1. The hereindescribed steelcontaining manganese substantially 1% to 2%; carbon below 1%; a substantial quantity of zirconium; and the hardnessand strength characteristic of such a composition in the aircooled condition.

2. The hereindescribed steel containing manganese substantially 1% to 2%; carbon below 1%; asubstantial quantity of zirconium; a phosphorus content not above normal; and a tensile strength less than 125,000 pounds per square inch.

3. The hereindescribed steel containing manganese substantially 1% to 2%; carbon 0.35 to 0.70%; zirconium 0.15 to 0.50%; a phosphorus content not above normal; and a tensile strength less than 125,000 pounds per square inch.

In testimony whereof, I aflix my signature.

FREDERICK M. BECKET. 

